Eastern Pacific Tropical Weather Discussion

000
AXPZ20 KNHC 230949
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1005 UTC THU MAY 23 2013

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0930 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS W FROM NICARAGUA AT 12N86W TO
13N99W...THEN SW THROUGH AN EMBEDDED 1010 MB LOW PRES NEAR
10.5N101.5W WITH THE TROUGH CONTINUING WSW TO 08N120W WHERE
SCATTEROMETER WINDS INDICATE AN ITCZ AXIS FORMS. THE ITCZ
EXTENDS NW TO 11N132W WHERE THE REMNANT TROUGH OF FORMER
TROPICAL CYCLONE ALVIN IS ANALYZED FROM 03N137W TO 13N133W.
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 120
NM OF 08N120W...AND 180 NM EITHER SIDE OF A LINE FROM 10N86W
TO 09N114W. SIMILAR CONVECTION HAS FORMED S OF THE ITCZ
WITHIN 30 NM EITHER SIDE OF A LINE FROM 06N127W TO 12N133W.

GUIDANCE IS SUGGESTING THE EMBEDDED SURFACE LOW AT 10.5N101.5W
WILL MOVE W ALONG THE MONSOON TROUGH AXIS TO NEAR 10N103W 
TONIGHT...NEAR 11N104W ON THU NIGHT AND NEAR 10N107W ON FRI 
NIGHT BUT NOT HAVE ANY SIGNIFICANT DEVELOPMENT.

AN ILL-DEFINED TROPICAL WAVE HAS MOVED INTO THE SW CARIBBEAN AND
IS EXPECTED TO SLOW AS IT MOVES ACROSS COSTA RICA ALONG THE
MONSOON TROUGH INTO THE EPAC LATE TONIGHT. GUIDANCE CONTINUES TO 
SUGGEST THE WAVE WILL HELP SPAWN A WEAK LOW PRESSURE NEAR 10N87W 
BY EARLY FRI. MODEL GUIDANCE IS SOMEWHAT IN AGREEMENT WITH THIS 
LOW FORMING AND MOVING SLOWLY W ALONG THE MONSOON TROUGH AXIS 
OVER THE WEEKEND. THE GFS MODEL CONTINUES TO BE MUCH MORE 
AGGRESSIVE THAN OTHER GUIDANCE...AND DEVELOPS THE LOW INTO A 
TROPICAL CYCLONE. I BLENDED AND SMALL PERCENTAGE OF THE LATEST 
GFS INTO THE PREVIOUS PACIFIC GRIDS...WHICH IN TURN CONSISTED OF 
A GFS AND ECMWF BLEND. I TONED DOWN THE WINDS AND WIND GUSTS 
CONSERVATIVELY TO A SLOWLY DEVELOPING LOW NEAR 09N93W LATE 
SUN...NEAR 11N95W LATE MON...AND NEAR 13N96W LATE TUE WITH 
CYCLONIC WINDS THEN AT 20-30 KT...WITH MAX SEAS TO ABOUT 18 FT.  

MODEL GUIDANCE CONTINUES TO SUGGEST THE NORTHERLY DRAINAGE FLOW 
WILL INCREASE TO 15-20 KT IN THE GULF OF TEHUANTEPEC ON FRI 
NIGHT AND PULSE AT 15-20 KT LATE AT NIGHT THROUGH SUNRISE EACH 
MORNING THROUGH THE WEEKEND. THE STRENGTH OF THESE DRAINAGE 
WINDS WILL BE HIGHLY INFLUENCED BY THE STRENGTH AND TRACK OF THE 
TROPICAL LOW TO THE S. EXPECT MANY FLUCTUATIONS IN THE GRIDS 
THROUGH THE EXTENDED PERIODS.   

A SURFACE RIDGE EXTENDS FROM NW TO SE FROM 32N136W TO 18N112W. 
NW WINDS ARE CURRENTLY AT 10-15 KT ALONG THE ENTIRE W SHORE OF 
THE BAJA CALIFORNIA PENINSULA WITH SEAS CURRENTLY AT 4-5 FT
EXCEPT 5-6 FT NEAR THE SOUTHERN TOP OF THE BAJA PENINSULA PER A 
RECENT ALTIMETER PASS. SEAS OF 6-8 FT PRIMARILY IN NW SWELL ARE 
EXPECTED TO REACH ALONG THE BAJA PENINSULA TO THE N OF 28N LATER 
TODAY...AND REACH AS FAR S AS 25N ON FRI. 

NORTHERLY WINDS AT 15-20 KT CONTINUE ACROSS THE N-CENTRAL 
PACIFIC WATERS FROM 24-30N BETWEEN 116W-140W WITH SEAS MAXING
AT 12-13 FT IN THE ASSOCIATED N SWELL ACROSS THE AREA FROM 
28-30N BETWEEN 118-124W. NOTE THAT N WINDS ARE AT 20-25 KT 
IN THE DISCUSSION WATERS FROM 30-32N BETWEEN 118-125W...WITH
SEAS 13-15 FT. ALTHOUGH N WINDS WILL BE ONLY IN THE 15-20 KT 
RANGE...THE N SWELL RESULTING IN SEAS TO 8 FT...WILL PROPAGATE S 
TO ALONG 10N W OF 115W BY LATE FRI NIGHT...THEN BEGIN TO SUBSIDE 
FROM THE NW ON SAT. 

NE TRADES CONTINUE ARE AT 15-20 KT WITHIN 240 NM W OF THE 
REMNANT TROUGH OF ALVIN. THE TROUGH IS EXPECTED TO CONTINUE TO 
SHIFT SLOWLY W REACHING FROM 11N140W TO 15N135W TONIGHT AND 
SHIFT W OF 140W ON FRI.

$$
NELSON